Signaling by electromagnetic waves



No. 752,895. PATBNTED FEB. 23, 1904. R. A. FESSBNDEN. SIGNALING BYELECTROMAGNETIC WAVES. I

APPLICATION FILED MAR. 14, 1903.

H0 MODEL.

m: mums Fcrcas car, omom-Lrmo wasamcmu. u c.

UNITED STATES Patented February 23, 1904.

PATENT ,OFFICE.

REGINALD A. FESSENDEN, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR,

BY DIRECT AND MESNE ASSIGNMENTS, TO THE NATIONAL-ELEC- TRIO SIGNALINGCOMPANY, OF PITTSBURG, PENNSYLVANIA, A COR- PORATION OF NEW JERSEY.

SIGNALING BY ELECTROMAGNETIC WAVES.

SPECIFICATION formingpart of Letters Patent No. 752,895, dated February23, 1904.

Application filed March 14, 1903. I

To all whom it may concern.-

Be it known that I, REGINALD A. FESSENDEN, a citizen of the UnitedStates, residing at Pittsburg, in the county of Allegheny and State ofPennsylvania, have invented or discovered certain new and usefulImprovements in Signaling by Electromagnetic Waves, of whichimprovements the following is a specification.

The invention described herein relates to certain improvements insignaling by electromagnetic waves, having for their object theprevention of external disturbances, so that stations may be workedsimultaneously while situated close to each other. This is accomplishedby arranging in suitable relation to the conductor of the station secondor auxiliary conductors so proportioned that the effect of waves emittedfrom the disturbing-station on the station-conductor proper will beopposed and neutralized by the effect of the disturbingwaves upon .theauxiliary conductor.

The invention is hereinafter more fully described and claimed.

In the accompanying drawing, forming a part of this specification, isshown a diagrammatic view illustrative of my invention.

In the practice of my invention the radiating-conductor 1 is connectedto one of the sparking terminals 2,-the other terminal being connectedto ground. While any suitable form or construction of generator, such asan induction-coil or a dynamo or a dynamo and transformer, as describedinmy previous patents, may be employed, the invention is illustrated forconvenience in connection with an induction-coil and battery. As shown,the terminals of the secondary of the inductioncoil 3 are connected,respectively, to the sparking terminals 2. The primary of theinduction-coil forms part of a circuit containing a battery I and amake-and-break mechanism independently operated at a predetermined rate.A convenient form of make-and-break mechanism consists of a cup 5,containing mercury, and a pin 6, movable into and out of the mercury. Asuitable means for reciprocating Serial No. 147,726. (No model.)

the pin consists of a small electric motor 7, having the pin soconnected to its armatureshaft as to be moved into and out of themercury during the rotation of the shaft. The rotation of the motor maybe controlled in any convenient manner, as by a tuning-fork 8, which iselectrically driven and controls by transformer is connected, as shownin Fig. 1,

in series with the conductor 1, the coils of the primary being arrangedfor convenience upon a glass jar 10, filled with kerosene. It ispreferred that this transformer should be arranged above the upperspar-king terminal 2. The secondary 1A of the transformer is wound on asmall glass jar 13, placed inside of the jar 10, and in series with thissecondary is arranged a suitable receiving apparatus 21, such as abarretter or other suitable receiving device, as described in'LettersPatent previously granted to me. In order to prolong the oscillations, aparallel-tunedIoircuit 22, containing a condenser, is connected in shuntto the sparking terminals, as described in Patent No. 706,735, grantedto me August 12, 1902. It has been found by experiment that the localcircuit 22 for prolonging the oscillations operates best when placed asnear the nodal point of oscillationrl. e. ,the groundas possible. Withhigh vertica1sfor example,

one hundred and fifty feet longwh ether the transformer is placed overor below the sparkgap makes little difference, as the length of wire onthe transformer is generally a moderately small fraction of the totalwave length. With lower verticals, havinga height of, say,

fifty feet, the length of wire between the sparkgap and the ground whenthe transformer is placed between sparkgap and ground hecomes a largerfraction of the total Wave length, and consequently the circuit 22 isrelatively farther away from the nodal point. With the type of verticalconsisting of single wire or a few wires, which was used at an earlydate by Marconi, the writer, and others and is still used in certaincombinations and-for certain purposes and in which the oscillations arepractically dead-beat, this displacement of the circuit 22 from nodalpoint is not of so much importance as when verticals having avery largecapacity, such as described in Patent No. 706,7 37, August 12, 1902,(large-capacity verticals,) giving prolonged oscillations, are used, forin this latter case if the circuit 22 is not near the nodal pointinterference is apt to be produced between the natural oscillations ofthe vertical and the oscillations of the secondary circuit 22. In suchcases it is thereforepreferred to place the transformer over thespark-gap instead of below, so as to bring the circuit 22 as near thenodal point as possible, in spite of the fact that there are certainadvantages in the opposite arrangement for example, the less liabilitytoshock and less liability to puncturing insulation.

A neutralizing-conductor 23, connected to ground, is arranged insuitable relation to the conductor 1. This conductor is preferablyshorter than the conductor 1 and has in series therewith the primary 24of a transformer, the secondary 25 of said transformer being in serieswith the secondary 14 of the transformer having its primary in serieswith the conductor 1. The neutralizing-conductor 23 is tuned to theperiod of the waves emitted by the dirturbing-station, thestation-conductor 1 being tuned to some other frequency. The height ofthe neutralizing-conductor 23 is so proportioned to the height of thestation-conductor 1 that with the particular frequency emitted by thedisturbing-station the currents generated in the secondaries 14 and 25will be equal. This can be done as though the conductor 1 is higher thanconductor 23. The lat: ter is in tune with the disturbing-station andthe station-conductor 1 is not. The secondaries 25 and 14 are so woundwith reference to each other that their currents would be in oppositedirections, and hence neutralize each other so far as their effect onthe receiver 21 is concerned.

The proportioning of the main and neutralizing conductors can beeffected by shortening the length of the neutralizing-conductor untilthe effect of the disturbing-waves thereon practically neutralizes theeffect of such waves on the main conductor 1. The same result may beobtained by making the conductor 23 of a fixed heighte. g., one-fifth ofthe height of the conductor 1and then changing the relative positions ofthe primary 24 and secondary 25 until, as before, the effects producedby the disturbing frequencies neutralize each other. The ability of theconductor 1 to respond to waves of a frequency to which it is not tuned,does not show that it has no marked period of its own, as no matter howsharply a conductor is tuned it will always respond to some extent towaves of a differ ent frequency. With reference to the values andproportions of the parts, if the conductor 1 has a height of one hundredand fifty (.150) feet it is found in practice with the arrangement shownthat one-fifth 1;) to one-tenth of the effect will be produced on it bythe disturbing frequency to which it is not tuned compared with theeffect of the frequency to which it is tuned. This ratio will of coursedepend greatly upon how near the disturbing frequency is to the resonantfrequency; but the foregoing corresponds approximately to conditionsfound in working. Under these conditions it is found that with a mainconductor 1 one hundred and fifty (150) feet high theneutralizing-conductor 23 should have a height of about thirty (30)feet, although as small a height as fifteen feet may be used. Preciseformula for the neutralizing-conductor cannot be given, for the reasonthat its dimensions will vary with the amount the oscillations areprolonged, the character of the receiver, the arrangement of theapparatus in the stations, and other details, such as the sharpness ofthe tuning. When very sharp tuning has been used, it has been foundpossible to shorten the length of the neutralizing-conductor to abouttwo feet long, the main conductor having a length of about one hundredand fifty feet; but under these conditions it is more difficult to keepit in adjustment. erate the apparatus as shown by altering the length ofthe neutralizing-vertical 23 until the desired efiect is produced. It isnot essential that the neutralization should be absolutely complete, aswith certain forms of receiveras, for example, with the barretterdescribed and shown in Letters Patent No. 7 06,7 44:, dated August 12,1902the neutralization is less complete than with the mechanicalreceivers of the type described in Letters Patent No. 706,736, datedAugust 12, 1902, and in application, Serial No. 125,030, filed September27, 1902'; but even when using the barretter the effect is markedlybeneficial, more especially when the indicating mechanism ismechanically tuned as described in application, Serial No. 121,173,filed August 27, 1902. It is possible that the inductive effect of theneutralizing conductor may cut down the strength of the signals; butsuch effect is very small, as the neutralizing-conductor is not onlyshorter than the main vertical, but it is also out of tune with theoscillations which it is desired to receive. Consequently since thenetralizing-conductor is one-fifth or less of the height of the mainconductor and on ac- It is, however, always possible to opcount of thereciprocal relation in tuning it is only aflected one-fifth as much bythe untuned as by the tuned the total effect of theneutralizing-conductor on the receiver as regards messages of the properperiodicity will be only one twenty-fifth (5;) as much as that of themain conductor.

WVhile the arrangement herein shown and described is desirable, I do notlimit myself to the particular form or construction of any of the partsor elements, as other forms of apparatus would readily suggestthemselves to those skilled in the art.

I claim herein as my invention 1. In a system of signaling byelectromagnetic waves, the combination at a station of two conductorsand a receiver for electromagnetic waves in operative relation to saidconductors, said conductors being adapted to oppose the efiects on thereceiver produced by disturbing electrical impulses while permittingwaves of the desired periodicity to affect the receiver, substantiallyas set forth.

2. In a system of signaling by electromagnetic waves, the combination ata station of two conductors one being tuned more closely to theperiod-of the disturbing impulses than the other, said conductors beingso arranged and proportioned as to exert equal and opposite efiects onthe receiver as regards impulses of the disturbing periodicities,substantially as set forth.

3. In a system of signaling by electromagnetic waves, the combination ata station of two aerial conductors and a receiver for electromagneticwaves in operative relation to said conductors, said conductors beingadapted to oppose the effects on the receiver produced mitting'waves ofthe desired periodicity to affect the receiver, substantially as setforth.

4. In a system of signaling by electromagnetic waves, the combination ata station of two conductors and a' receiver for electromagnetic waves inoperative relation to said conductors, said conductors being adapted tooppose the effects on the receiver produced by disturbing electricalimpulses while permitting waves of the desired periodicity to afl'ectthe receiver, and a mechanically-tuned receiver, substantially as setforth.

5. In a system of signaling by electromagnetic waves, the combination ata station of two conductors one being tuned more closely to the periodof the disturbing impulses than the other, said conductors being soarranged and proportioned as to exert equal and opposite efi'ects on thereceiver as regards impulses of the disturbing periodicities, and amechanically-tuned receiver, substantially as set forth.

6. In a system of signaling by electromagnetic waves, the combination ata station of two aerial conductors one being more closely tuned to theperiod of the disturbing impulses than the other, said conductors beingso arranged and proportioned as to exert equal and opposite eifects onthe receiver as regards impulses of the disturbing periodicities.'

In testimony whereof I have hereunto set my hand.

REGINALD A. FESSENDEN.

Witnesses:

JEssIE BENT, CHAS. O, KEYSER.

